As it is now, they aren’t being taught and they’re not learning from what the AI is producing because they don’t understand it. The produced code is a black box, and the AI’s development is a black box too. All they know is that running it produces something like what they asked for. They have no idea about failure modes which is a fundamental concept of engineering. The worst part is that AI is covering up their deficiencies. They don’t know what skills they lack. They don’t even know what skills are required because they haven’t put the effort in.
There are obviously good junior engineers that are using AI judiciously and not as a crutch. They’re the ones who still interact with seniors to get help and actually learn. They would have been successful without AI too. These are the ones the author is talking about. In my experience, the momentum is moving towards the worse type of junior the more AI is adopted. Unless that changes, it will erase their value.